Noise reduction for dslr

[Starcrazzy]

Hi guys,
I have been useing the dsi for a while now and have had a little sucess...I recently got hold of a canon 10d..Does anyone have any ideas for getting rid of exess noise from the longer exposures??or mabye a dark subtract method??im not sure...i havn't had a clear night yet to check it out..
cheers

[Vermin (Tom)]

More stacked exposures will reduce the noise by the square root of the number of frames.

As for software, you could try Neatimage, however in my opinion it does tend to make images look a little soft (even if not used aggressively).

EDIT: also you can try a mild Gaussian blur in the colour channel (usually the red ch) that has the worst noise using Photoshop.

[Striker (Tony)]

For starters does the 10D have noise reduction under the advanced option or setting..if so select this..what it will do will double your exposure time for every image taken..meaning if you take 1 minute exposure it will take 2 minutes to finish the image as it is taking the dark frame immediately after the exposure.

In the long run you are far better off taking multiple dark frame and combining them to make a master then subtracting these from the image but that takes a lot more time initially and experience with software.

[[1ponders] (Paul)]

Starcrazzy, what, if any, astroimaging programs do you have atm. Do you have Photoshop?

If we know what you have it will help in deciding what is the best way to approach your problem.

The bottom line is if your camera has in built noise reduction, us it to start with. It may not be the best approach, though there is a certain amount of uncertainty about that atm, but you will at least get images that are a lot less noisey.

If it doesn't have noise reduction then you will need to take dark frames and use them to calibrate your light frames to remove some of the electronic noise. Taking a dark frame is easy. As soon after taking your lights as possible cover your scope objective or remove the camera from the scope, replace the lens and put the lens cap on and take three but preferably at least 9 or 10 covered shots at the same length of them as your lights. It's important to take the darks as close to the lights time as possible as the noise is ambient temp dependant. If the current temp is 25 deg you want to take the darks at 25 deg, not 22 deg as there will be less noise at 22 deg.

Once you have your darks they are then converted to a single master dark which is used on each light frame to reduce the electronic/heat noise. How this is done will depend on the programs you have. If you don't have any then consider IRIS. It's a great program, it's free and does a top job. Many people shy away from it because it is command line driven but if you get and read Jim Solomon's cook book ( Jim Solomon's Astrophotography Cookbook for Iris )it will give you a good start. Plus it will help you to understand what you are ultimately trying to achieve.

[Starcrazzy]

wow...thanx guys...i have photoshop,registax and iprep...i didnt know you could just take dark frames like that...i will have to try that, and i have seen a function in registax for loading darks...perhaps this is the way to remove them from the image....do i combine the images first and then subtract the darks??or what?...thanx again ....u gu ys rock

[Striker (Tony)]

You need to apply the dark frames to each image before combining....or if you use the in camera noise reduction it is already done for you.